The present invention relates to electronic cameras (commonly called as digital still camera) in which a plurality of image pickup signals of different exposure amount read out from a single image pickup device are synthesized to obtain an image having a wide dynamic range.
Although solid-state image pickup devices such as CCD image pickup device are used in such image pickup apparatus as TV camera, video camera, electronic camera, etc., there is a problem that the dynamic range of a solid-state image pickup device is much narrower than that of a silver salt photographic film.
To eliminate this problem, there have been proposed techniques in which an image having an increased dynamic range is obtained by synthesizing two image pickup signals of different exposure amount read out from a single image pickup device. For example, Japanese patent application laid open No.4-207581 discloses those constructed as follows.
In particular, one of those disclosed therein comprises an image pickup device including a light receiving section having a plurality of light receiving elements for photoelectric conversion of optical information and a means for transferring signals from the light receiving section. Immediately after performing a first exposure at the light receiving section and transmitting signals of the first exposure to the transfer means, a second exposure having a longer exposure time than the first exposure is started. After outputting signals of the first exposure from the image pickup device, signals of the second exposure are transmitted to the transfer means to output signals of the second exposure from the image pickup device. The second exposure is thereby performed in the period during which signals of the first exposure are outputted from the image pickup device so as to make smaller a temporal difference in picture taking caused by such plurality of times of exposure. In this aspect, a disclosure is also made with respect to one in which the first exposure time is controlled by transmitting of signals due to the exposure from the light receiving section to the transfer means, i.e., by an electronic shutter function, while the second exposure time is controlled by a means for shutting off light to control an exposure time of the image pickup device. The second exposure time can thus be controlled independently from the transferring operation of the first exposure signals.
Further, one as shown in FIG. 1 is disclosed in Japanese patent application laid open No.6-141229 as a construction for synthesizing two image pickup signals that are different in exposure amount to synthesize an image having a wide dynamic range. In particular, signals with a shorter charge accumulating period CS1 read out from CCD 501 are recorded at memory 502, and the recorded signals are read out from the memory 502 at substantially the same timing as readout from CCD 501 of signals with a longer charge accumulating period CL1. The signals read out from the memory 502 are multiplied by CL1/CS1 for example xe2x80x9c4xe2x80x9d using a multiplier 503. By this multiplication using such factor, signal levels of those signals differing from each other in charge accumulating period with respect to the same object are theoretically brought to the same level.
Next, a level weighting means H 505 assigns a weight corresponding to signal level to the signal of charge accumulating period CS1 from the multiplier 503. A weight is assigned also to the signal of charge accumulating period CL1 at a level weighting means L 504. The characteristics of the respective weights are shown in FIG. 2 where abscissa represents an input signal level and ordinate represents a weighting factor to be assigned to the signals. The level weight L is a weight of 1 for input levels up to 80%, is linearly lowered in weight value for 80% to 100% and puts the weighting factor to 0 at the input level of 100%. The level weight H, on the other hand, is a weight of 0 for levels up to 80%, is linearly increased in weight value for 80% to 100% and puts the weighting factor to 1 at the input level of 100%. The weighting factor is always 1 for input levels of 100% and above. The image signals differing from each other in dynamic range are weighted thus and are synthesized as added together at an adder 506 to form a single piece of image. The portions in good conditions (with favorable S/N and without saturation) are extracted through this weighting process to synthesize an image having a wide dynamic range. Since the synthesized image is processed at a rate about twice the normal when signals are read out from CCD 501, the scanning rate of signals is converted at a rate converter 507 to xc2xd so that it corresponds to a standard TV signal. Further, while the signal level of the synthesized image at its maximum is 400%, the level is compressed to 100% at a level compression means 508. It should be noted that numeral 509 in FIG. 1 denotes a timing control section.
In this manner, a difference in signal level due to difference in charge accumulating period is corrected with respect to the two signals that are different in charge accumulating period. A larger weight is assigned to those portions where signals are not saturated while an adequate S/N is kept to make a selection from these image signals and at the same time to smoothly synthesize the two image signals. The signal obtained as having a wide dynamic range and an increased signal amplitude is then outputted after compressed to a standard signal level. An image having an increased dynamic range is thereby synthesized from the two image signals having been controlled with respect to their charge accumulating periods at CCD of which dynamic range is narrow.
Further, Japanese patent application laid open No.62-108678 discloses a technique in which, when an image having a wide dynamic range is to be obtained by synthesizing two image pickup signals that are different in exposure amount, one of the image pickup signals is picked up by using only natural light while the other image pickup signal is generated by a picture taking process using a strobe light. These image pickup signals are compared with each other and the portions of greater signal are outputted to obtain a synthesized image.
Furthermore, a disclosure i s made in Japanese Patent Publication No.2659570 with respect to an electronic still camera in which, at the same time of causing strobe light to emit for a plurality of times, a plurality of times of readout of charge are effected within a time period for taking one frame of picture so that amount of light to be received is adjusted by control of an emission amount of strobe light or an electronic shutter operation of solid-state image pickup device so as to increase dynamic range without a saturation in output of the solid-state image pickup device even in high luminance regions.
Referring now to the above Japanese patent application laid open No.4-207581, it discloses a technique where, of two image pickup signals that are different in exposure amount, an image of smaller exposure amount is picked up first in time by using an electronic shutter function of the image pickup device and, then, an image of greater exposure amount is picked up while controlling the charge accumulating time using a means for shutting off light (mechanical shutter). If, however, a means for shutting off light is employed in an electronic camera, such means for shutting off light is normally kept in its opened state. A charge accumulating time is controlled by a transition from the opened state to its closed state. In this case, therefore, the charge accumulating time differs from one position to another on the light receiving surface of the image pickup device. A shading thus results. In the disclosure of the above publication, however, this point is not taken into consideration at all and a means for preventing a shading is not mentioned either. There is another problem that, in respect of control of charge accumulating period, a means for shutting off light is not very accurate when compared to an electronic shutter of the image pickup device.
Furthermore, in the techniques disclosed in the above publications, an accuracy is not taken into consideration in setting an exposure amount ratio of two image pickup signals when the two image pickup signals of different exposure amount are to be obtained. The problems in the case of using a flash emission means are not mentioned either.
In particular, if the luminance of the object of picture is at a relatively low level, picture taking is performed by using a strobe light in combination. In forming a synthesized image having a wide dynamic range through a synthesis of two image pickup signals of different exposure amount, if an attempt is made to simply synthesize the obtained two image pickup signals where one of the image pickup signals is generated by using natural light alone and the other of the image pickup signals by a strobe light in combination, it is difficult due to the intrinsically large variance of a strobe light, even with a constant exposure time, to attain a precise correspondence between the two image pickup signals in order to achieve a predetermined ratio of their exposure amounts. Further, in the case of using a strobe light, while image pickup signal having a predetermined exposure ratio in relation to the image pickup signal picked up by natural light alone can be obtained at the portions within a picture frame reached by the strobe light, image pickup signal in the portions not reached by the strobe light is of the same exposure amount as one picked up by natural light alone. The predetermined exposure ratio cannot be obtained. Furthermore, in the case of synthesizing image pickup signal by natural light and image pickup signal by a strobe light, since these are the image pickup signals different from each other in white balance, there is a problem that color balance is partially lost in the synthesis. Moreover, in the case of image pickup apparatus such as an electronic camera including an exposure setting means (AE), a white balance setting means (WB), a gain control means, a stop control means, etc., when two image pickup signals of different exposure amount are synthesized to obtain an image having a wide dynamic range, no consideration is taken as to how to achieve a correspondence between them.
Further, while the above Japanese patent application laid open No.6-141229 discloses a technique in which synthesis is smoothly performed while changing the weighting factor when two image pickup signals of different exposure amount are synthesized to synthesize an image having a wide dynamic range, the problem of false color in synthesizing a color image is not considered and no disclosure is made with respect to the problems in using a strobe.
To eliminate the above described problems of the conventional image pickup apparatus in which a plurality of image pickup signals that are different from each other in amount of exposure are synthesized to form an image having a wide dynamic range, it is a first object of the present invention to provide an electronic camera capable of correcting shading occurring in obtaining image pickup signal of a larger exposure amount by controlling charge accumulating time of image pickup device using a means for shutting off light.
In accordance with the present invention, there is provided an electronic camera including a single image pickup device having an electronic shutter function capable of desirably controlling exposure amount by controlling charge accumulating time and means for shutting off light from a light receiving surface of the image pickup device. After generating an image pickup signal of smaller exposure amount by using the electronic shutter function of the image pickup device, an image pickup signal of larger exposure amount is generated by controlling charge accumulating time of the image pickup device by the means for shutting off light, the two image pickup signals being synthesized to obtain an image having an increased wide dynamic range. Control of charge accumulating time of the image pickup device by the means for shutting off light is effected by operation from opened state to closed state of the means for shutting off light. Shading correction means is provided for correcting shading resulting from difference in charge accumulating time among the pixels of the image pickup device occurring due to the operation toward closed state of the means for shutting off light.
By providing such shading correction means, it is possible to correct shading resulting from difference in charge accumulating time among the pixels from one position to another on the light receiving surface of the image pickup device due to the operation from opened state to closed state of the means for shutting off light, so as to prevent an occurrence of false color in the synthesized image. The above first object is thereby achieved.
It is another object of the present invention to provide an electronic camera in which shading is not caused even when an image pickup signal is generated by effecting control of charge accumulating of the image pickup device by the means for shutting off light.
In accordance with the present invention, there is provided an electronic camera including a single image pickup device having an electronic shutter function capable of desirably controlling exposure amount by controlling charge accumulating time and means for shutting off light from a light receiving surface of the image pickup device. After generating an image pickup signal of smaller exposure amount by using the electronic shutter function of the image pickup device, an image pickup signal of larger exposure amount is generated by controlling charge accumulating time of the image pickup device by the means for shutting off light, the two image pickup signals being synthesized to obtain an image having an increased wide dynamic range. The means for shutting off light is constituted by a focal-plane shutter. Shutter charge of the focal-plane shutter is effected immediately after a completion of electronic shutter""s operation of the image pickup device, in the state where charge accumulating operation of the image pickup device is halted. After completion of the shutter charge, charge accumulating operation of the image pickup device is started such that control of the charge accumulating time is effected by a normal focal-plane shutter operation.
By thus using a focal-plane shutter as the means for shutting off light and causing it to operate in the manner described above, no shading occurs in image pickup signal obtained by controlling charge accumulating time by means of the focal-plane shutter""s operation. Accordingly, it is possible to obtain a synthesized image free from shading without providing a shading correction means even when a focal-plane shutter is used. The above object is thereby achieved.
It is still another object of the present invention to provide an electronic camera capable of accurately controlling charge accumulating time even when a charge accumulating time of image pickup device of a relatively long time period is to be controlled.
In accordance with the present invention, there is provided an electronic camera including: a single image pickup device having an electronic shutter function capable of desirably controlling exposure amount by controlling charge accumulating time; means for shutting off light from a light receiving surface of the image pickup device; means for generating from the image pickup device two image pickup signals of the same object differing from each other in exposure amount; and synthesizing means for obtaining an image having an increased wide dynamic range by performing synthesis of the two image pickup signals obtained by the means for generating image pickup signal. The means for generating image pickup signal is adapted to generate image pickup signal of larger exposure amount by controlling charge accumulating time of the image pickup device by the means for shutting off light after generating image pickup signal of smaller exposure amount by using the electronic shutter function of the image pickup device if charge accumulating time of the image pickup device for obtaining image pickup signal of larger exposure amount is set as shorter than a period required for readout of all the pixels of the image pickup device. Also, it is adapted to generate image pickup signal of larger exposure amount by using the electronic shutter function of the image pickup device instead of the means for shutting off light, if charge accumulating time of the image pickup device for obtaining image pickup signal of larger exposure amount is set as longer than the time period required for readout of all the pixels of the image pickup device.
By constructing in this manner, an electronic shutter can be used in setting of charge accumulating time, if charge accumulating time of the image pickup device for generating image pickup signal of larger exposure amount is set as longer than the time period required for readout of all the pixels of the image pickup device. In such case, charge accumulating time can be accurately controlled by using the electronic shutter which is more accurate than the means for shutting off light. The above object is thereby achieved.
It is yet another object of the present invention to provide an electronic camera capable of accurately controlling exposure amounts of image pickup signals so as to attain an exposure amount ratio corresponding to a previously set exposure amount ratio between two shots of picture taking.
In accordance with the present invention, there is provided an electronic camera having a function for performing synthesis of two image pickup signals obtained by performing by a single image pickup device two shots of picture taking of different exposure amount of the same object to obtain an image having an increased wide dynamic range, further including a photometric device having a separate entity from the image pickup device and means for setting charge accumulating time of the image pickup device at the second shot of picture taking so that it corresponds to a previously set exposure amount ratio of the two shots of picture taking based on an exposure amount measured by the photometric device at the first shot of picture taking.
By thus setting charge accumulating time at the second shot of picture taking based on an exposure amount at the first shot of picture taking measured by a photometric device, it is possible to accurately control an exposure amount ratio between the two image pickup signals. The above object is thereby achieved.
It is a further object of the present invention to provide an electronic camera in which, when two image pickup signals of different exposure amount are generated by using flash emission means and are synthesized to obtain an image having a wide dynamic range, time difference in generation of the two image pickup signals is reduced so as to obtain images where difference due to the time difference in generation between the two image pickup signals is relatively small.
In accordance with the present invention, there is provided an electronic camera having a function for performing synthesis of two image pickup signals obtained by performing by a single image pickup device two shots of picture taking of different exposure amount of the same object to obtain an image having an increased wide dynamic range, further including flash emission means. The flash emission means is caused to emit at one or both of a timing in the second half of charge accumulating time of the image pickup device at the first shot of picture taking and a timing in the first half of charge accumulating time of the image pickup device at the second shot of picture taking.
By constructing in this manner, time difference of generation in generating two image pickup signals of different exposure amount by using a flash emission means can be reduced so that images be obtained as having a smaller difference due to time difference of generation between the two image pickup signals. The above object is thereby achieved.
In this aspect, it may further include a photometric device having a separate entity from the image pickup device and means for causing the flash emission means to emit at both of the two shots of picture taking so as to set charge accumulating time of the image pickup device at the second shot of picture taking based on an emission amount ratio of the two emissions measured by the photometric device. By thus setting charge accumulating time of the second shot of picture taking based on an emission amount ratio of the two emissions measured by the photometric device, it is possible to accurately control an exposure amount ratio of the two image pickup signals even when flash emission means is used.
Also, in this aspect, the image pickup device may be provided with an electronic shutter function capable of desirably controlling an exposure amount by controlling charge accumulating time. The flash emission means is caused to emit at both of the two shots of picture taking and, at a smaller emission of the two emissions of the flash emission means, timing for stopping the smaller emission may be set as the same as timing for terminating an electronic shutter operation of the image pickup device.
In general, proportion of surplus emission in a flash emission means is larger for a smaller flash emission amount. Accordingly, by setting as in the above the stop timing of smaller emission of the flash emission means as the same as the ending timing of an electronic shutter operation of the image pickup device, the smaller emission is not affected by an surplus emission so that image pickup signals are obtained as having an accurate exposure amount ratio where an influence of surplus emission in the case of using a flash emission means is reduced.
It is a further object of the present invention to provide an electronic camera in which, when two image pickup signals of different exposure amount are synthesized to obtain an image having a wide dynamic range, the two image pickup signals are obtained as having the same depth of field.
In accordance with the present invention, there is provided an electronic camera having a function by which two image pickup signals obtained by performing by a single image pickup device two shots of picture taking of different exposure amount of the same object are synthesized to obtain an image having an increased wide dynamic range, further including means for setting diaphragm stop value of lens fixed at the two shots of picture taking.
By thus performing the two shots of picture taking of different exposure amount with the diaphragm stop of lens being fixed by the lens diaphragm stop value fixing means, the two image pickup signals are obtained as having the same depth of field. The above object is thereby achieved.
In this aspect, exposure setting means may be provided such that a diaphragm stop value and/or shutter speed obtained by the exposure setting means before taking picture be used at the picture taking for obtaining the image pickup signal of larger exposure amount and, at the picture taking for obtaining the image pickup signal of smaller exposure amount, the same diaphragm stop value be used while shutter speed be set in such a manner as to correspond to a previously set exposure amount ratio of the two shots of picture taking. It is also possible to construct the exposure setting means such that an exposure value be set based on photometric output of a photometric device provided separately from the image pickup device or to construct the exposure setting means such that an exposure value be set based on image pickup signal of the image pickup device. By thus providing an exposure setting means and using a diaphragm stop value obtained by the exposure setting means as fixed at the two shots of picture taking, it is possible to obtain image pickup signals at an optimum exposure having the same depth of field.
It is a further object of the present invention to provide an electronic camera in which, when two image pickup signals of different exposure amount are generated and synthesized to form an image having a wide dynamic range, it is possible to obtain the synthesized image without producing a false color due to difference in white balance.
In accordance with the present invention, there is provided an electronic camera having a function by which two image pickup signals obtained by performing by a single image pickup device two shots of picture taking of different exposure amount of the same object are synthesized to obtain an image having an increased wide dynamic range, further including means for performing white balance correction by setting the same white balance correction value for the two image pickup signals of different exposure amount before the synthesis.
By thus providing white balance correction means to perform white balance correction by setting the same correction value for the two image pickup signals of different exposure amount before the synthesis, the synthesized image is obtained as having a wide dynamic range without producing a false color due to difference in white balance. The above object is thereby achieved.
In this aspect, white balance setting means may be provided such that white balance correction value obtained by the white balance setting means before picture taking be used in white balance correction by the white balance correction means. By thus using a white balance correction value obtained by the white balance setting means, it is possible to obtain the synthesized image even more accurately without producing a false color due to difference in white balance.
Also, in this aspect, the correction value to be used in the white balance correction means may be set based on image pickup signal before performing the synthesis. By thus setting a white balance correction value based on the image pickup signal before performing the synthesis, the synthesized image can be obtained as even more accurately corrected of white balance.
Furthermore, in this aspect, the correction value to be used in the white balance correction means may be set based on the image pickup signal of larger exposure amount of the two image pickup signals of different exposure amount before performing the synthesis. In general, while white balance correction is required to be performed for the portion to become an essential part of the object, the portion to become an essential part is more likely to be included in the image pickup signal of larger exposure amount. Accordingly, by setting white balance correction value based on the image pickup signal of larger exposure amount, a synthesized image of which white balance is corrected can be obtained efficiently.
It is a further object of the present invention to provide an electronic camera in which a synthesized image having a wide dynamic range can be efficiently obtained without producing a false color due to difference in white balance.
In accordance with the present invention, there is provided an electronic camera having a function by which two image pickup signals obtained by performing by a single image pickup device two shots of picture taking of different exposure amount of the same object are synthesized to obtain an image having an increased wide dynamic range, further including means for correcting white balance with respect to the synthesized image having a wide dynamic range.
By thus correcting white balance with respect to the synthesized image, a synthesized image having a wide dynamic range can be efficiently obtained without an occurrence of false color due to difference in white balance. The above object is thereby achieved.
In this aspect, white balance setting means may be provided such that white balance correction value obtained by the white balance setting means before picture taking be used in white-balance correction by the white balance correction means. By thus using a white balance correction value obtained by the white balance setting means, the synthesized image can be obtained efficiently and accurately without an occurrence of false color due to difference in white balance.
Also, in this aspect, the correction value to be used in the white balance correction means may be set based on the synthesized image having a wide dynamic range, or the correction value to be used in the white balance correction means may be set based on image pickup signal before performing the synthesis. By thus setting a white balance correction value, the synthesized image can be obtained as efficiently and accurately corrected with respect to white balance.
Furthermore, in this aspect, the correction value to be used in the white balance correction means may be set based on the image pickup signal of larger exposure amount of the two image pickup signals of different exposure amount before performing the synthesis. By thus setting white balance correction value based on the image pickup signal of larger exposure amount, a synthesized image having a wide dynamic range can be obtained as more efficiently corrected with respect to white balance.
It is a further object of the present invention to provide an electronic camera in which, when two image pickup signals of different exposure amount are generated and synthesized to obtain an image having a wide dynamic range, the two image pickup signals are readily generated as suitably corresponding at a high accuracy to a previously set exposure amount ratio.
In accordance with the present invention, there is provided an electronic camera having a function by which two image pickup signals obtained by performing by a single image pickup device two shots of picture taking of different exposure amount of the same object are synthesized to obtain an image having an increased wide dynamic range, further including gain control means such that gain values at the gain control means for the two image pickup signals are respectively set to values that are different from each other.
By thus setting the gain values corresponding to the respective image pickup signals by the gain control means, it is possible to readily generate the two image pickup signals suitably corresponding to an exposure amount ratio at a high accuracy. The above object is thereby achieved.
In this aspect, the gain values for the two image pickup signals are set so that the exposure amount ratio of the two image pickup signals corresponds to a previously set exposure amount ratio. By constructing in this manner, even when shutter speeds cannot accurately correspond to a previously set exposure amount ratio, the gain values can be adjusted to readily generate the two image pickup signals which accurately correspond to the exposure amount ratio.
It is a further object of the present invention to provide an electronic camera in which, when two image pickup signals of different exposure amount are synthesized to form an image having a wide dynamic range, the two image pickup signals of different exposure amount can be readily generated from an image pickup device by charge accumulating time of the same duration.
In accordance with the present invention, there is provided an electronic camera having a function by which two image pickup signals obtained by performing by a single image pickup device two shots of picture taking of different exposure amount of the same object are synthesized to obtain an image having an increased wide dynamic range, further including diaphragm control means such that the two image pickup signals of different exposure amount are generated by changing diaphragm stop value of lens by the diaphragm control means.
By constructing in this manner, two image pickup signals of different exposure amount can be readily generated by charge accumulating time of the same duration, thereby achieving the above object.
In this aspect, means for correcting peripheral attenuation of lens may be provided such that correction with respect to peripheral attenuation which occurs as a result of difference in diaphragm stop value of lens be performed for the two image pickup signals of different exposure amount generated by changing diaphragm stop value of lens by the diaphragm control means. When two image pickup signals of different exposure amount are generated by changing diaphragm stop value of lens by the diaphragm control means, a difference in peripheral attenuation occurs by different diaphragm stop values and a false color is produced in the synthesized image. However, a synthesized image without an occurrence of false color resulting from a difference in peripheral attenuation can be obtained by correcting the difference in peripheral attenuation of lens by providing the means for correcting peripheral attenuation of lens in the above described manner.
Also, in this aspect, flash emission means may be provided such that two image pickup signals of different exposure amount be generated by effecting flash emissions of the same emission amount and changing the diaphragm stop value of lens by the diaphragm stop value control means at two shots of picture taking of different exposure amount. By constructing in this manner, it is not necessary to control flash emission amount and it becomes possible to equalize an exposure amount ratio by flash emissions and an exposure amount ratio by ambient light.
It is a further object of the present invention to provide an electronic camera in which, when a plurality of color image signals of different exposure amount are synthesized to form a synthesized color image having a wide dynamic range, the synthesized color image can be formed without producing a false color or pseudo contour.
In accordance with the present invention, there is provided an electronic camera having color image synthesizing means for forming a color image having a wide dynamic range by synthesizing a plurality of color image signals of different exposure amount, further including weighting means for assigning weights to the plurality of color image signals corresponding to their respective signal level and means for adding the plurality of weighted color image signals such that the weighting means sets the same weighting factor respectively for each color signal in the plurality of color image signals.
By thus effecting weighted addition by respectively setting the same weighting factor to each color signal of the plurality of color image signals, a synthesized color image having a wide dynamic range can be formed without producing a false color or pseudo contour. The above object is thereby achieved.
It is a further object of the present invention to provide an electronic camera in which, even when flash emission is used, image pickup signals can be readily generated as having a predetermined exposure amount ratio in every part in a frame of picture and a synthesized image having a wide dynamic range can be obtained as preserving a uniform white balance in every part in the frame of picture.
In accordance with the present invention, there is provided an electronic camera including: optical means for forming an optical image of the object of picture taking; image pickup means for generating image pickup signals by taking picture and effecting photoelectric conversion of an image of the object formed at the optical means; flash emission means for illuminating the object; exposure condition designating means for designating exposure conditions at the image pickup means; image pickup signal synthesizing means for synthesizing two image pickup signals from two separate shots of picture taking at the image pickup means by exposure conditions designated by the exposure condition designating means; flash emission control means for controlling emission of the flash emission means in connection with the exposure conditions for each shot at the time of the two shots of picture taking; and control means for controlling operation of each of the means in the above.
By thus using flash emission for both of the two shots of picture taking, it is possible to equalize an exposure amount ratio by normal light and an emission amount ratio by flash emission in every part in a frame of picture and it is also readily possible to make uniform white balance in the synthesized image. The above object is thereby achieved.
In one aspect of the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, the exposure condition designating means includes one or both of electronic shutter means for desirably controlling exposure amount by controlling photoelectric charge accumulation of the image pickup means and light shut off means for shutting off light from a light receiving surface of the image pickup means such that the control means controls one or both of the electronic shutter means and the light shut off means, and the flash emission means to make an emission amount ratio by light from the flash emission means as the same as an exposure amount ratio by normal light excluding the light from the flash emission means at the two shots of picture taking.
By constructing in this manner, exposure amount ratios in the regions dominated by exposure by normal light and in the regions dominated by exposure by flash emission of the flash emission means can be equalized at the two shots of picture taking using flash emission, thereby a synthesized image is obtained as having an improved image quality.
In this aspect, the exposure amount ratio by normal light of the two shots of picture taking is set by ratio of photoelectric charge accumulating time of the two shots at the image pickup means. By constructing in this manner, ratio of exposure amount by normal light can readily be set in the case where ratio of emission amount by normal light and ratio of emission amount by light from the flash emission means are to be equally set between the two shots of picture taking.
In another aspect of the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, the flash emission means includes single charge storage means for accumulating emission energy of the flash emission means such that the total of emission amounts at the two shots of picture taking of the flash emission means is set equal to or lower than the total emission energy of the single charge storage means. It is thereby possible to effectively use charge of the single charge storage means when light by the flash emission means is used at the two shots of picture taking.
In still another aspect of the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, the flash emission means includes a plurality of charge storage means differing from each other in capacitance value for accumulating emission energy of the flash emission means such that a full emission of the flash emission means is caused at each shot of the two shots of picture taking by selectively using the plurality of charge storage means so as to make a difference in the total capacitance values to be respectively used. By thus causing a full emission of the flash emission means at the two shots of picture taking, image pickup signals at an accurate emission amount ratio can be obtained without requiring an emission amount control (dimming control).
In yet another aspect of the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, the flash emission means includes a plurality of charge storage means for accumulating emission energy of the flash emission means such that one picture taking is performed by a smaller emission based on a full emission using one single or a plurality of charge storage means and the other picture taking is performed by a larger emission based on an emission under dimming control using the other single or plurality of charge storage means. By constructing in this manner, the smaller emission can be caused to emit accurately by a full emission without requiring dimming control and the larger emission is caused to emit under dimming control so as to be able to desirably set an emission amount ratio.
In a further aspect of the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, the flash emission means includes a plurality of charge storage means for accumulating emission energy of the flash emission means such that one picture taking is performed by a smaller emission based on an emission under dimming control using one single or plurality of charge storage means and the other picture taking is performed by a larger emission based on a full emission using the other single or plurality of charge storage means. Thereby, the smaller emission is caused to emit under dimming control so as to be able to desirably set an emission amount ratio and the larger emission can be caused to emit accurately by a full emission without requiring dimming control.
In a further aspect of the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, the flash emission means includes at least one charge storage means for accumulating emission energy of the flash emission means such that the two shots of picture taking are performed as illuminated by a smaller emission and a larger emission each based on an emission under dimming control. By thus using an emission under dimming control for both of the two shots of picture taking, due to the fact that full emission is not used, it is not necessarily required to provide a separate individual emission means for each and the value of emission amount ratio can be set more freely.
In this aspect, the dimming control may be effected by control of emission time of the flash emission means. By thus effecting dimming control, a setting of emission amount can be accurately performed without requiring a photometry means.
Also, in this aspect, a photometry means may be provided such that the dimming control is effected based on detection of a predetermined emission amount by direct photometry of the photometry means. In the case where dimming control is effected in this manner, an actual emission amount can be measured so that control of light be effected to achieve a required emission amount in accordance with a reflectance of the object.
Furthermore, in this aspect, the dimming control may be effected based on measurement and detection of a predetermined voltage at the charge storage means. By constructing in this manner, dimming control can be effected without using a photometry means and voltage measuring means at the charge storage means for dimming control can be used in common with the voltage measuring means of charging circuit of the charge storage means.
Moreover, in this aspect, when dimming is to be effected of the flash emission means at the second shot of picture taking, an emission amount of light from the flash emission means at the first shot of picture taking is measured and an emission amount under dimming control of the flash emission means at the second shot is set based on the measured emission amount so as to correspond to a previously set emission amount ratio of the flash emission means between the two shots of picture taking. By constructing in this manner, since variance in the first emission amount of the flash emission means is actually measured and such variance can be corrected and absorbed at the setting of the controlled second emission amount, accuracy of the emission amount ratio can be improved.
Further, in the case where, as in the above, variance in the first emission amount is actually measured and such variance is corrected at the setting of the controlled second emission amount, a photometry means is provided so that the emission amount of the flash emission means at the first shot of picture taking is measured by direct photometry of the photometry means. By constructing in this manner, the first actual emission of the flash emission means can be measured so that a required emission amount in accordance with reflectance of the object be obtained to accurately set the second emission amount.
Furthermore, in the case where, as in the above, variance in the first emission amount is actually measured and such variance is corrected at the setting of the controlled second emission amount, the emission amount of the flash emission means at the first shot of picture taking is obtained by a voltage measurement at the charge storage means. By constructing in this manner, the first emission amount of the flash emission means can be measured without using a photometry means and voltage measuring means at the charge storage means for the measurement of emission amount can be used in common with the voltage measuring means of charging circuit of the charge storage means.
In a further aspect of the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, an emission amount of the flash emission means is measured to obtain an emission amount ratio based on such emission amounts and the exposure amount ratio by normal light is set as the same as such emission amount ratio. By constructing in this manner, variance in the emission amount of the flash emission means can be absorbed to obtain an accurate emission amount ratio and, by setting an exposure amount ratio equal to such emission amount ratio, a synthesized image can be obtained as having high image quality where the emission amount ratio and the exposure amount ratio are accurately matched.
In this aspect, an emission amount ratio may be obtained by measuring an emission amount of the flash emission means at a first shot of picture taking and by computing a second emission amount by calculation based on the first emission amount. Thereby, an emission amount ratio can be obtained only by the measurement of the first emission amount so that an exposure amount ratio be determined before the second emission.
Also, in this aspect, an emission amount ratio may be obtained by measuring emission amounts of the flash emission means at the first and second shots of picture taking. By constructing in this manner, a more accurate emission amount ratio can be obtained based on a result of actual emissions.
Furthermore, in this aspect, a photometry means may be provided so as to measure an emission amount of the flash emission means based on direct photometry by the photometry means. By constructing in this manner, an actual emission by the flash emission means can be readily measured and an emission amount ratio can be accurately obtained by acquiring a required emission amount in accordance with the reflectance of the object.
Moreover, in this aspect, an emission amount of the flash emission means may be obtained by a voltage measurement at the charge storage means. By constructing in this manner, an emission amount of the flash emission means can be measured without using a photometry means and voltage measuring means at the charge storage means for the measurement of emission amount can be used in common with the voltage measuring means of charging circuit of the charge storage means.
In accordance with the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, the flash emission means comprises one xenon emission tube and one charge storage means and is caused to emit at the two shots of picture taking by using the one xenon emission tube and the one charge storage means. By constructing in this manner, the flash emission means can be constructed as having a small circuitry size.
In accordance with the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, the flash emission means comprises one xenon emission tube, a plurality of charge storage means and charge storage means switching means and is caused to emit at the two shots of picture taking by using the one xenon emission tube and at least one of the charge storage means switched and selected by the charge storage means switching means. In the case of such construction, since a plurality of units of charge storage means are provided, it is possible to respectively control a smaller emission and a larger emission by using charge storage means provided exclusively for each. Each emission can be performed independently so that an accurate emission control be effected without reciprocally affected by each other.
In accordance with the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, the flash emission means comprises a plurality of xenon emission tubes, one charge storage means and xenon emission tube switching means and is caused to emit at the two shots of picture taking by using at least one xenon emission tube switched and selected by the xenon emission tube switching means and the one charge storage means. By constructing in this manner, since a plurality of units of the xenon emission tube are provided, no reciprocal effect occurs of consecutive emission at the two shots of picture taking and, therefore, the emissions can be effected respectively at a high accuracy irrespective of interval between emissions.
In accordance with the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, the flash emission means comprises a plurality of xenon emission tubes, a plurality of charge storage means, xenon emission tube switching means and charge storage means switching means and is caused to emit at the two shots of picture taking by using at least one xenon emission tube switched and selected by the xenon emission tube switching means and at least one charge storage means switched and selected by the charge storage means switching means. By constructing in this manner, since a plurality of units of charge storage means are provided, it is possible to respectively control a smaller emission and a larger emission by using charge storage means provided exclusively for each and the emissions are not reciprocally affected because both can be performed independently. Also, since a plurality of units of the xenon emission tube are provided, no reciprocal effect occurs of two consecutive emissions and the emissions can be effected respectively at a high accuracy irrespective of interval between emissions.
In this aspect, the charge storage means may be constituted by one main capacitor. By constructing in this manner, circuitry size can be reduced.
Also, in this aspect, the charge storage means may be constituted by a plurality of main capacitors connected in parallel. By constructing in this manner, capacitance of a single main capacitor can be reduced so that its production is easier. Also, for example, by making capacitance of each main capacitor as the same as that of others to equalize ratio of the number of capacitors to be used in a smaller emission to the number of capacitors to be used in a larger emission and ratio of their emission amounts (exposure amount ratio), a required emission amount ratio can be controlled in an emission time of the same duration so that control is simpler.
In a further aspect of the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, the respective emissions of the flash emission means at the two shots of picture taking are each effected as a single emission. By thus effecting the emissions at the two shots of picture taking respectively by a single emission, control of emission is easier and variance in emission amounts can be reduced.
In a further aspect of the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, the respective emissions of the flash emission means at the two shots of picture taking are effected either as one unit emission and a collection of a plurality of times of unit emission or each as a collection of a plurality of times of unit emission. In such construction, since ratio of emitting units corresponds to a required, desirable emission amount ratio (exposure amount ratio) by setting an emission amount per unit emission to a certain fixed value, an advantage is achieved that the emission amount ratio can be controlled by the number of emitting units. Also, emission amount measuring means may additionally be provided to measure an emission amount of each unit emission of the collection of a plurality of unit emissions so that an accurate emission amount ratio be obtained by adjusting and controlling a total emission amount.
In a further aspect of the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, the respective emissions of the flash emission means at the two shots of picture taking are effected as a smaller emission and a larger emission in that order. By thus effecting the smaller emission first, control of the emission amount of the larger emission is easier, since the voltage drop at the main capacitor of the charge storage means at start of the larger emission is relatively small. As a result, accuracy in the emission amount ratio can be improved. Also, in the case where the two emissions are consecutively effected by the same flash emission means, some extent of reciprocal effect occurs between the emissions. Since such effect produces a larger effect in the emission with a greater absolute value, the effect can be mitigated to an extent possible by effecting the smaller emission first.
In a further aspect of the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, range finding means is provided such that an emission of the flash emission means is controlled to an optimum emission amount corresponding to a distance information obtained by the range finding means. By thus using a distance information, an emission amount can be set more accurately.
In this aspect, the emission to be controlled correspondingly to the distance information is a smaller emission. While variance in emission of the smaller emission is hard to be controlled by a real time emission control such as based on direct photometry of a photometric device or voltage measurement at the charge storage means, it can be caused to emit relatively accurately by effecting a unitary emission by setting an absolute value of emission amount based on a distance information.
In a further aspect of the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, pre-photometry means is provided such that an emission of the flash emission means is controlled by using a pre-photometry information obtained by the pre-photometry means. By thus using a pre-photometry information where an actual luminance of the object is measured, an absolute value of emission amount of a quantity of light corresponding to the luminance of the object can be obtained so that an absolute value of emission amount can be set at a high accuracy without using a distance information.
In a further aspect of the present invention, of the above electronic camera for generating a synthesized image having a wide dynamic range by using flash emission in combination, pre-photometry means is provided such that an emission of the flash emission means is controlled by using a pre-photometry information obtained at the pre-photometry means by causing a pre-emission of the flash emission means.
Since an emission amount is thus set based on a pre-photometry information which involves an additional actual emission of the flash emission means, a more precise absolute value of the emission amount can be obtained.
In this aspect, the pre-photometry means may be formed by an external photometry means. By constructing in this manner, an absolute value of emission amount of a quantity of light corresponding to the luminance of an object can be obtained by using a photometry information of the actual object, and the external photometry means of the pre-photometry means can be used in common as the photometry means for emission of the flash emission means.
Also, in this aspect, the pre-photometry means may be used in common as the image pickup means. By constructing in this manner, a separate, external photometry means is not required and an absolute value of emission amount of a quantity of light corresponding to the luminance of an object can be obtained by using a photometry information of the actual object.